In a sigma bonded organometallic compounds, there is a sigma bond between metal atom and any one of the carbon atom of the hydrocarbon part of molecule
Examples would be Grignard Reagent (RMgX); Frankland reagent (R2Zn) and  R3Al.
Try reviewing your bonding concepts from NCERT or any reference book

Hey Likhesh,

I found a YouTube video, the link of which is posted below. They are quite a few examples in it. I hope you find it helpful.

https://youtu.be/rmzDGfO4fME

Hey 

Zigler natta catalyst and frankland  are two examples of sigma bounded organometallic compound .for more examples go through your ncert book